A copy of the sound a few thousandths of a second behind, swept back and forth and fed back into itself. The delay is short enough that the copy does not repeat what came in but cancels against it, in a row of notches that slide up and down as the sweep moves — the jet-aircraft sound, and what separates it from the chorus is the feedback: each pass round sharpens the notches into ringing peaks. Below nothing the feedback is subtracted instead, which is the hollower version of the same effect. Delay is the shortest the sweep gets and Depth how far above that it goes, so the sweep never reaches back past the delay itself; Rate is how quickly, and is an input as well as a knob. Dry level is what came in and Wet level the swept copy, summed rather than crossfaded — a flanger needs both to cancel against each other, and at no dry there is nothing for the copy to cancel with and the effect disappears. The sweep starts at three milliseconds because a delay that feeds back cannot be shorter than one block of processing in a browser, which is where the thin, close-up flanging of a tape machine would have been. Feedback is an input as well, with a depth for how far a signal there moves it, and what reaches the loop is held inside the knob's own range, so the notches can be swept from hollow to ringing without the loop running away.
Four notes played on Keys, passing through it on their way out.
ATMOSYNTH built-in module